Maven Error « Could not find Launcher »

If you have the following error when launching a Maven command, for example « mvn install »:

Could not find the main class: org.codehaus.plexus.classworlds.launcher.Launcher

Your are probably using a Maven 2 configuration for a Maven 3 usage. Delete your global variable M2_HOME and it should work. You can use M3_HOME instead to select the folder for the « repository » of dependencies, and the emplacement of the configuration file settings.xml.